1. Field of the Invention
The present invention relates to a coordinate input apparatus for inputting the coordinate value of a position on a display screen of a display unit disposed in a computer system or the like.
2. Description of the Prior Art
A display unit is disposed in a computer system for effecting data input/output operations. A cursor or an indication symbol (to be collectively called as a cursor herebelow) is used as a mark to indicate a processing objective position on a display screen of the display unit. Various kinds of coordinate input apparatuses are used to move the cursor to an arbitrary coordinate position in the display screen. Among such apparatuses, those called, for example, a mouse, a joystick, a track ball are generally capable of moving the cursor in an arbitrary direction on the display screen through a move operation in an operation section and are quite efficient in practice because the operation thereof is easy.
In general, a mouse is an apparatus having three bearings disposed on the bottom thereof and is operated by use of these bearings which roll on a desk, thereby obtaining a coordinate value from a rotation angle of the bearings. A joystick is generally an apparatus having a control bar, which is grasped and is inclined by the operator to an arbitrary position toward a front, rear, right, or left direction, thereby obtaining a coordinate value. In addition, a track ball includes a ball rotatable in any direction, which is rotated by a palm, a finger tip, or the like, thereby obtaining a coordinate value from a rotation angle of the ball. When a move operation is conducted, these apparatuses each simultaneously output a signal indicating an amount of movement in the X axis and a signal indicating an amount of movement in the Y axis, which determine the direction and amount of the movement of the cursor. The computer receives as inputs these movement signals in the respective axes and then controls the movement of the cursor on the display screen according to the received signals. For the control of cursor movement, the ratio of the amount of cursor movement to the amount of movement in the operation section is beforehand determined, and thus the cursor movement is controlled in proportion to the amount of movement in the operation section according to the ratio.
As the reference for the above-mentioned techniques, there have been the Japanese Patent Application Laid -Open Nos. 58-149535, 58-129643, 59-111524, and 59-22126, Japanese Utility Model Registration Application laid-open Nos. 57-29941, 59-6240, and 58-90433.
A coordinate position on a display screen is specified in various cases such as where a relatively fine position is specified, namely, a fine adjustment is effected and where a relatively long distance from an end of the display screen to a position, for example, an opposing end thereof is specified, namely, a coarse adjustment is achieved. That is, in a case of the fine adjustment, the amount of cursor movement is required to be made smaller as compared with the amount of movement in the operation section of the coordinate input apparatus, whereas in the coarse adjustment, the amount of cursor movement is required to be made greater as compared with the movement in the operation section. These requirements are mutually contradictory and therefore cannot be satisfied in the conventional system in which the ratio of the cursor movement to the movement in the operation section is fixed. The ratio of the cursor movement can be changed by a setting operation in a program or the like, and there are some systems having a special apparatus such as a switch, so that the ratio of the cursor movement is changed through an operation of the switch. However, this requires a particular operation, and it is quite troublesome for the operator to conduct this kind of operation during the coordinate specifying job.